In dual-band systems, such as systems that include a local multipoint distribution service (LMDS), which generally operates between 27.5 and 31.3 GHz, and E-band mode, which generally operates between 71 and 86 GHz, the range of communication is limited by the linearity (e.g., transmit power) of the higher frequency band (e.g., E-band). This is because at high frequencies, it is difficult to provide sufficient linear power and path loss is relatively high. Further, the local oscillator (LO) frequency is also high and requires high LO power to drive an E-band mixer. As a result, the LO lineup design is analogous to implementing another high power/frequency transmitter, which is very costly.
In contrast to the LO lineup design, it is relatively easy to obtain high power for devices that operate in the LMDS band (27.5-31.3 GHz) as compared with a high mmW frequency band, such as E-band. Previous approaches referred to as “sliding LO” architectures suffer from several drawbacks, including imaging problems, being limited in frequency selection, involve complicated frequency planning, and require a high powered LO drive.
In a dual-band microwave/millimeter-wave (mmW) transceiver design, the local oscillator (LO) is difficult to design because the LO frequency is related to the mmW carrier frequency. Therefore, the power required to drive the mmW mixer is very high.